tandem crank question

i've been shopping the internet for a new set of cranks for my road bike and i keep coming across "tandem cranks." i understand how a tandem works, but is there any difference between a tandem crank and a regular double crank, other than the chainring(s)?

before posting, a "noob" should always ask themselves "could this have been answered by first visiting Sheldon Brown

A tandem's crossover crankset's left-hand cranks will have crank spiders for the timing rings / sync chain that transmit the captain's power from the front crankset to the rear crankset along the tandem's left side. The right front crank has no spider... just as the left-hand crank does on a single bike.

Converted single bike cranks used on a tandem require applying loctite to the pedal threads, or installing a helicoil to change the threading on 3 of the crankarms. So, if you want to use a captains crank you will need to do that.

If you use a stoker crankset, you will not need to change anything, but you may wish to remove the timing ring.

An engineer whom I trust suggests 'countertapping' the existing threading. This way you have two threadings in one crank - both left-hand and right-hand. Mount the pedal with some Loctite and you're ready. The thickness of a crank (very roughly 1 cm) gives a secure hold.